The certificate of `rcn-ee.com' is not trusted.

I was attempting to help a student update the bootloader on his BeagleBone Black and get the following

./update_bootloader.sh

Bootloader Recovery

Downloading Device’s Bootloader

Opps, my key expired:

Let's Encrypt Authority X3
Issued On
Wednesday, November 21, 2018 at 6:31:42 PM
Expires On
Tuesday, February 19, 2019 at 6:31:42 PM

Sorry, i just renewed it, so you should be good now.

Regards,